Semiconductor light emitting element, manufacturing method thereof, integrated semiconductor light emitting device, manufacturing method thereof, image display device, manufacturing method thereof, illuminating device and manufacturing method thereof

ABSTRACT

A semiconductor light emitting element, manufacturing method thereof, integrated semiconductor light emitting device, manufacturing method thereof, illuminating device, and manufacturing method thereof are provided. An n-type GaN layer is grown on a sapphire substrate, and a growth mask of SiN, for example, is formed thereon. On the n-type GaN layer exposed through an opening in the growth mask, a six-sided steeple-shaped n-type GaN layer is selectively grown, which has inclined crystal planes each composed of a plurality of crystal planes inclined from the major surface of the sapphire substrate by different angles of inclination to exhibit a convex plane as a whole. On the n-type GaN layer, an active layer and a p-type GaN layer are grown to make a light emitting element structure. Thereafter, a p-side electrode and an n-side electrode are formed.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. application Ser. No.10/512,131 filed on Oct. 21, 2004, which was a National Stage ofInternational Application No. PCT/JP04/001952 filed on Feb. 19, 2004,and which claims priority to Japanese Patent Document No. P2003-077703filed on Mar. 20, 2003.

BACKGROUND

This invention relates to a semiconductor light emitting element,manufacturing thereof, integrated semiconductor light emitting device,manufacturing method thereof, image display device, manufacturing methodthereof, illuminating device and manufacturing method thereof, which areespecially suitable for application to light emitting diodes usingnitride III-V compound semiconductors.

A light emitting diode as a semiconductor light emitting element hasbeen proposed. This semiconductor light emitting element was made bygrowing an n-type GaN layer on a sapphire substrate; next formingthereon a growth mask having a predetermined opening; selectivelygrowing an n-type GaN layer in form of a six-sided pyramid having aninclined crystal plane inclined from the major surface of the substrate,i.e. having an S-oriented plane; and growing an active layer, p-type GaNlayer and other layers on the inclined crystal plane (see, for example,brochure of International Publication No. 02/07231 Wages 47-50 and FIGS.3-9)). This light emitting diode can prevent propagation of penetratingdislocations from the substrate side to layers composing the elementstructure, and can improve the crystalline property of these layers,high emission efficiency can be obtained.

FIGS. 1A and 1B show a typical semiconductor light emitting elementdisclosed in the above-mentioned literature. This semiconductor lightemitting element is manufactured by the following method. An n-type GaNlayer 102 is first grown on a sapphire substrate 101 having a C+oriented major surface. After that, a SiO2 film is formed on the entiresurface of the n-type GaN layer 102, and it is patterned by lithographyand etching to make a growth mask 104 having an opening of apredetermined geometry in a position for forming the element. Thegeometry of the opening 103 is a circle or a hexagon having one sideparallel to the <11-20>direction. Size of the opening 103 is about 10μm. In the next step, under the existence of the growth mask 104, ann-type GaN layer 105 is selectively grown on a part of the n-type GaNlayer 102 exposed through the opening 103. As a result of the selectivegrowth, the n-type GaN layer 105 is in form of a six-sided pyramid. Sixplanes of the six-sided pyramidal n-type GaN layer 106 are S-orientedplanes inclined from the major surface of the sapphire substrate 101.After that, an active layer 106 composed of InGaN compounds, forexample, and a p-type GaN layer 107 are sequentially grown on the n-typeGaN layer 105. Through these steps, here is obtained adouble-hetero-structured light emitting diode structure including thesix-sided pyramidal n-type GaN layer 105, active layer 106 and p-typeGaN layer 107, the last two being grown sequentially on the inclinedcrystal planes of the six-sided pyramidal n-type GaN layer 105. In thenext step, which is not explained here in detail, a p-side electrode isformed on the p-type GaN layer 107 and an r-side electrode is formed onthe n-type GaN layer.

Existing semiconductor light emitting elements, having a light emittingelement structure made by selectively growing the six-sided pyramidaln-type GaN layer 105 having an S-oriented inclined crystalline plane andnext growing the active layer 106 and the p-type GaN layer 107 on theS-oriented plane, were unsatisfactory in light emitting efficiency, andinevitably required a large occupied area per each element.

SUMMARY

The present invention in an embodiment provides a semiconductor lightemitting element sufficiently high in light emitting efficiency andsmall in occupied area per each element, as well as a manufacturingmethod of the semiconductor light emitting element.

The present invention in another embodiment provides an integratedsemiconductor light emitting device sufficiently high in light emittingefficiency and small in occupied area per each element, a manufacturingmethod thereof, an image display device, a manufacturing method thereof,an illuminating device and a manufacturing method thereof.

In an embodiment of the invention is a semiconductor light emittingelement comprising:

a semiconductor layer of a first conduction type which is formed on amajor surface and includes a convex crystal portion having an inclinedcrystal plane composed of a plurality of crystal planes inclined fromthe major surface by different angles of inclination to exhibit a convexplane as a whole;

at least an active layer and a semiconductor layer of a secondconduction type which are sequentially layered at least on the inclinedcrystal plane of the crystal portion;

a first electrode electrically connected to the semiconductor layer ofthe first conduction type; and

a second electrode formed on the semiconductor layer of the secondconduction type on the crystal portion and electrically connected to thesemiconductor layer of the second conduction type.

Materials of the semiconductor layer of the first conduction type,active layer and semiconductor layer of the second conduction type caninclude any suitable material. However, materials having a wurtzitecrystalline structure are typically used. Examples of semiconductorshaving a wurtzite crystalline structure are nitride III-V compoundsemiconductors. In addition, II-VI compound semiconductors such asBeMgZnCdS compound semiconductors and BeMgZnCdO compound semiconductorscan be given as such examples. Most widely, nitride III-V compoundsemiconductors are composed of AlxByGa1-x-y-zInzAsuN1-u-vPv (where0≦x≦1, 0≦y≦1, 0≦z≦1, 0≦u≦1, 0≦v≦1, 0≦x+y+1<1 and 0≦u+v≦1). More specificexamples are composed of AlxByGa1-x-y-zInzN (where 0≦x≦1, 0≦y≦1, 0≦z≦1and 0≦x+y+1<1). Typical examples are composed of AlxGa1-x-zInzN (where0≦x≦1 and 0≦z≦1). Examples of nitride III-V compound semiconductorsinclude GaN, InN, AlN, AlGaN, InGaN, AlGaInN, and the like.

In case the semiconductor layer of the first conduction type has awurtzite crystalline structure, the plurality of crystal planes asconstituents of the inclined crystal plane of the convex crystal portionof the semiconductor layer are typically S-oriented planes (includingplanes that can be regarded S-oriented planes substantially). Angles ofinclination of the crystal planes as constituents of the inclinedcrystal planes become smaller from the bottom of the crystal portiontoward the apex. This crystal portion typically has a steeple-shapedconfiguration, which is six-sided most typically. In this case, anglesof inclination of the uppermost crystal planes of the crystal portion,i.e. the upper parts of the crystal planes involving the apex of thecrystal portion, which compose the inclined crystal planes, arepreferably in the range from about 3 μm to about 20 μm, or typically inthe range from about 10 μm to about 15 μm.

In another embodiment, the present invention includes a method ofmanufacturing a semiconductor light emitting element having: asemiconductor layer of a first conduction type which is formed on amajor surface and includes a convex crystal portion having an inclinedcrystal plane composed of a plurality of crystal planes inclined fromthe major surface by different angles of inclination to exhibit a convexplane as a whole; at least an active layer and a semiconductor layer ofa second conduction type which are sequentially layered at least on theinclined crystal plane of the crystal portion; a first electrodeelectrically connected to the semiconductor layer of the firstconduction type; and a second electrode formed on the semiconductorlayer of the second conduction type on the crystal portion andelectrically connected to the semiconductor layer of the secondconduction type, comprising:

growing a first semiconductor layer of the first conduction type on asubstrate;

forming a growth mask having an opening at a predetermined position onthe first semiconductor layer;

selectively growing a second semiconductor layer of the first conductiontype on the first semiconductor layer exposed through the opening in thegrowth mask; and

sequentially growing at least the active layer and the semiconductorlayer of the second conduction type to cover the second semiconductorlayer.

In an embodiment, the entirety of the first semiconductor layer of thefirst conduction type and the second semiconductor layer of the firstconduction type corresponds to the semiconductor layer of the firstconduction type.

In general, any material may be used as the substrate provided itassures a good crystallographic property when the first semiconductorlayer of the first conduction type, second semiconductor layer of thefirst conduction type, active layer, semiconductor layer of the secondconduction type, and so forth, are grown thereon. More specifically,here is usable a substrate made of sapphire (Al2O3) (includingC-oriented plane, A-oriented plane and R-oriented plane), SiC (including6H, 4H and 3C), nitride III-V compound semiconductors (such as GaN,InAlGaN, AlN, and the like), Si, ZnS, ZnO, LiMgO, GaAs, MgAl2O4 or thelike. Preferably, a hexagonal crystalline substrate or a cubiccrystalline substrate of one of those materials is used, but a hexagonalcrystalline substrate is more preferable. In case the firstsemiconductor layer of the first conduction type, second semiconductorlayer of the first conduction type, active layer and semiconductor layerof the second conduction type arc made of nitride III-V compoundsemiconductors, a sapphire substrate having a C-oriented plane as itsmajor surface may be used. The term “C-oriented plane” or the likeherein includes any crystalline plane that slightly inclines therefromup to about 5 to about 6° and can be regarded as the C-oriented planesubstantially.

For growth of the first semiconductor layer of the first conductiontype, second semiconductor layer of the first conduction type, activelayer and semiconductor layer of the second conduction type, metalorganic chemical vapor deposition (MOCVD), hydride vapor phase epitaxyor halide vapor phase epitaxy (HVPE), for example,,may be used. Toensure that the inclined crystal plane of the convex crystal portionmakes a good convex plane composed of a plurality of crystal planesdifferent in angle of inclination, growth temperature for selectivegrowth of the second semiconductor layer of the first conduction typeamong those layers is controlled preferably within the range from about920° C. to about 960° C., more preferably within the range from about920° C. to about 950° C., or still more preferably around about 940° C.Growth rate for the selective growth is controlled preferably at orabove 6 μm/h, or more preferably in the range from about 6 μm/h to about18 μm/h. For growth of the active layer and the semiconductor layer ofthe second conduction type, growth temperatures are typically controlledlower by about 20° C. to about 40° C. or more, for example, than thegrowth temperature of the second semiconductor layer of the firstconduction type.

Basically, the growth mask may be made of any material providednucleation on the growth mask is amply less than nucleation on the firstsemiconductor layer (in other words, growth on the growth mask isprevented), and selective growth is therefore assured. Typically,however, a silicon oxide nitride (SiON) film, silicon nitride (SiN(especially Si3N4) film or their lamination is used as the growth mask.Otherwise, the growth mask may be an aluminum oxide (Al2O3) film,tungsten (W) film and a laminated film combining any of these films andany of the above-mentioned films. To assure that the secondsemiconductor layer becomes a good steeple-shaped or pyramidalconfiguration, especially six-sided, the growth mask is preferably amask at least with its top surface being made of silicon nitride, suchas a mask made of a silicon nitride film or a mask made by stacking asilicon nitride film on a silicon oxide film.

The opening of the growth mask may have any geometry. Typically,however, it is hexagonal or circular. In case the opening of the growthmask is hexagonal, at lest one side of the hexagon is preferably normalto the <1-100> direction or <11-20> direction to prevent that thesemiconductor layer grown by using the growth mask deviates from thehexagon.

Size of the opening in the growth mask (maximum measure in the directionparallel to the major surface of the substrate) is preferably small toreduce the area occupied by the element. However, if it is excessivelysmall, it tends to invite crystal defects such as dislocations,depositional defects or the like during selective growth of the secondsemiconductor layer. Taking these factors into consideration, size ofthe opening in the growth is roughly in the range from about ¼ to about1 time the size of the semiconductor light emitting element. Forexample, it is in the range from about 2 μm to about 13 μm. If aslightly smaller size is preferable, the size of the opening istypically in the range from about 2 μm to about 5 μm or more preferablyin the range from about 2.5 μm to about 3.5 μm. If a slightly largersize is preferable, the size of the opening is typically in the rangeabout 7 μm to about 13 μm or more preferably in the range from about 9μm to about 11 μm.

Typically, the second semiconductor layer is selectively grown to spreadhorizontally wider than the opening of the growth mask. However, this isnot an indispensable requirement, but the second semiconductor layer maybe grown within the limit of the opening.

Typically, the second semiconductor layer is selectively grown so that asteeple-like configuration is formed. However, after the secondsemiconductor layer is selectively grown such that a crystal planesubstantially parallel to the substrate is formed on its top portion, anundoped semiconductor layer may be grown on the top portion. Thereby, incase the second electrode is formed on the semiconductor layer of thesecond conduction type whereas the first electrode is formed on thesemiconductor layer of the first conduction type comprising the firstsemiconductor layer and the second semiconductor layer and a current issupplied between the first electrode and the second electrode, theundoped semiconductor layer grown to form the apex portion of thesteeple-shaped crystal portion functions as a current blocking portionto prevent the current from flowing thereto. Since the crystallinequality of the apex portion of the crystal portion is usually inferiorto the other portion, this structure enables the current to flowbypassing the apex portion of the crystal portion assures that thecurrent flows only through the other portion having a good crystallinequality, and contributes to enhancing the emission efficiency.

The growth mask is usually left also after completion of the selectivegrowth. However, it may be removed after the selective growth. In thiscase, a step of removing the growth mask intervenes between the step ofselectively growing the second semiconductor layer of the firstconduction type on the first semiconductor layer in the opening of thegrowth mask and the step of sequentially growing at least the activelayer and the semiconductor layer of the second conduction type to coverthe second semiconductor layer.

In an embodiment, the present invention provides is an integratedsemiconductor light emitting device including a plurality of integratedsemiconductor light emitting elements each comprising:

a semiconductor layer of a first conduction type which is formed on amajor surface and includes a convex crystal portion having an inclinedcrystal plane composed of a plurality of crystal planes inclined fromthe major surface by different angles of inclination to exhibit a convexplane as a whole;

at least an active layer and a semiconductor layer of a secondconduction type which are sequentially layered at least on the inclinedcrystal plane of the crystal portion;

a first electrode electrically connected to the semiconductor layer ofthe first conduction type; and

a second electrode formed on the semiconductor layer of the secondconduction type on the crystal portion and electrically connected to thesemiconductor layer of the second conduction type.

To assure that the inclined crystal plane of each convex crystal portionexhibits a good convex plane composed of a plurality of crystal planesdifferent in angle of inclination, size of each opening of the growthmask is preferably in the range from about ¼ to about 1 time the size ofeach semiconductor light emitting element, in general. Morespecifically, it is in the range from about 2 μm to about 13 μm. If aslightly smaller size is desirable, it is typically in the range fromabout 2 μm to about 5 μm, or preferably in the range from about 2.5 μmto about 3.5 μm. If a slightly larger size is desirable, it is typicallyin the range from about 7 μm to about 13 μm, or preferably in the rangefrom about 9 μm to about 11 μm. Distance between openings of the growthmask is generally a double or more of the size of each semiconductorlight emitting element. More specifically, it is about 10 μm or more,preferably about 13 μm or more, or typically in the range from about 13μm to about 30 μm.

The integrated semiconductor light emitting device can be used for anypurpose. Its typical applications will be image display devices andilluminating devices, for example. The integrated semiconductor lightemitting device contemplates both a device including a plurality ofsemiconductor light emitting elements monolithically formed on a commonsubstrate and a device including a plurality of semiconductor lightemitting elements that are first monolithically formed on a commonsubstrate, then divided to discrete elements and then mounted on anothersubstrate.

In yet another embodiment, the present invention provides a method ofmanufacturing an integrated semiconductor light emitting deviceintegrating a plurality of integrated light emitting elements eachhaving a semiconductor layer of a first conduction type which is formedon a major surface and includes a convex crystal portion having aninclined crystal plane composed of a plurality of crystal planesinclined from the major surface by different angles of inclination toexhibit a convex plane as a whole; at least an active layer and asemiconductor layer of a second conduction type which are sequentiallylayered at least on the inclined crystal plane of the crystal portion; afirst electrode electrically connected to the semiconductor layer of thefirst conduction type; and a second electrode formed on thesemiconductor layer of the second conduction type on the crystal portionand electrically connected to the semiconductor layer of the secondconduction type, comprising:

growing a first semiconductor layer of the first conduction type on asubstrate;

forming a growth mask having openings at predetermined positions on thefirst semiconductor layer;

selectively growing a second semiconductor layer of the first conductiontype on the first semiconductor layer exposed through the openings inthe growth mask; and

sequentially growing at least the active layer and the semiconductorlayer of the second conduction type to cover the second semiconductorlayer.

In still yet another embodiment, the present invention provides an imagedisplay device including a plurality of semiconductor light emittingelements each comprising:

a semiconductor layer of a first conduction type which is formed on amajor surface and includes a convex crystal portion having an inclinedcrystal plane composed of a plurality of crystal planes inclined fromthe major surface by different angles of inclination to exhibit a convexplane as a whole;

at least an active layer and a semiconductor layer of a secondconduction type which are sequentially layered at least on the inclinedcrystal plane of the crystal portion;

a first electrode electrically connected to the semiconductor layer ofthe first conduction type; and

a second electrode formed on the semiconductor layer of the secondconduction type on the crystal portion and electrically connected to thesemiconductor layer of the second conduction type.

In a further embodiment, the present invention provides a method ofmanufacturing an image display device integrating a plurality ofintegrated light emitting elements each having a semiconductor layer ofa first conduction type which is formed on a major surface and includesa convex crystal portion having an inclined crystal plane composed of aplurality of crystal planes inclined from the major surface by differentangles of inclination to exhibit a convex plane as a whole; at least anactive layer and a semiconductor layer of a second conduction type whichare sequentially layered at least on the inclined crystal plane of thecrystal portion; a first electrode electrically connected to thesemiconductor layer of the first conduction type; and a second electrodeformed on the semiconductor layer of the second conduction type on thecrystal portion and electrically connected to the semiconductor layer ofthe second conduction type, comprising:

growing a first semiconductor layer of the first conduction type on asubstrate;

forming a growth mask having openings at predetermined positions on thefirst semiconductor layer;

selectively growing a second semiconductor layer of the first conductiontype on the first semiconductor layer exposed through the openings inthe growth mask; and

sequentially growing at least the active layer and the semiconductorlayer of the second conduction type to cover the second semiconductorlayer.

In still a further embodiment, the present invention provides anilluminating device having a single semiconductor light emitting elementor a plurality of integrated semiconductor light emitting elements eachcomprising:

a semiconductor layer of a first conduction type which is formed on amajor surface and includes a convex crystal portion having an inclinedcrystal plane composed of a plurality of crystal planes inclined fromthe major surface by different angles of inclination to exhibit a convexplane as a whole;

at least an active layer and a semiconductor layer of a secondconduction type which are sequentially layered at least on the inclinedcrystal plane of the crystal portion;

a first electrode electrically connected to the semiconductor layer ofthe first conduction type; and

a second electrode formed on the semiconductor layer of the secondconduction type on the crystal portion and electrically connected to thesemiconductor layer of the second conduction type.

In another embodiment, the present invention provides a method ofmanufacturing an illuminating device having a single semiconductor lightemitting element or a plurality of integrated semiconductor lightemitting elements each including: a semiconductor layer of a firstconduction type which is formed on a major surface and includes a convexcrystal portion having an inclined crystal plane composed of a pluralityof crystal planes inclined from the major surface by different angles ofinclination to exhibit a convex plane as a whole; at least an activelayer and a semiconductor layer of a second conduction type which aresequentially layered at least on the inclined crystal plane of thecrystal portion; a first electrode electrically connected to thesemiconductor layer of the first conduction type; and a second electrodeformed on the semiconductor layer of the second conduction type on thecrystal portion and electrically connected to the semiconductor layer ofthe second conduction type, comprising:

growing a first semiconductor layer of the first conduction type on asubstrate;

forming a growth mask having an opening at a predetermined position onthe first semiconductor layer;

selectively growing a second semiconductor layer of the first conductiontype on the first semiconductor layer exposed through the opening in thegrowth mask; and

sequentially growing at least the active layer and the semiconductorlayer of the second conduction type to cover the second semiconductorlayer.

In an embodiment, the present invention provides a semiconductor lightemitting element comprising:

a semiconductor layer of a first conduction type which is formed on amajor surface and includes a convex crystal portion having an inclinedcrystal plane exhibiting a substantially convex plane as a whole;

at least an active layer and a semiconductor layer of a secondconduction type which are sequentially layered at least on the inclinedcrystal plane of the crystal portion;

a first electrode electrically connected to the semiconductor layer ofthe first conduction type; and

a second electrode formed on the semiconductor layer of the secondconduction type on the crystal portion and electrically connected to thesemiconductor layer of the second conduction type.

In an embodiment, the present invention provides a method ofmanufacturing a semiconductor light emitting element having: asemiconductor layer of a first conduction type which is formed on amajor surface and includes a convex crystal portion having an inclinedcrystal plane exhibiting a substantially convex plane as a whole; atleast an active layer and a semiconductor layer of a second conductiontype which are sequentially layered at least on the inclined crystalplane of the crystal portion; a first electrode electrically connectedto the semiconductor layer of the first conduction type; and a secondelectrode formed on the semiconductor layer of the second conductiontype on the crystal portion and electrically connected to thesemiconductor layer of the second conduction type, comprising:

growing a first semiconductor layer of the first conduction type on asubstrate;

forming a growth mask having an opening at a predetermined position onthe first semiconductor layer;

selectively growing a second semiconductor layer of the first conductiontype on the first semiconductor layer exposed through the opening in thegrowth mask; and

sequentially growing at least the active layer and the semiconductorlayer of the second conduction type to cover the second semiconductorlayer.

In an embodiment, the present invention provides an integratedsemiconductor light emitting device including a plurality of integratedsemiconductor light emitting elements each comprising:

a semiconductor layer of a first conduction type which is formed on amajor surface and includes a convex crystal portion having an inclinedcrystal plane exhibiting a substantially convex plane as a whole;

at least an active layer and a semiconductor layer of a secondconduction type which are sequentially layered at least on the inclinedcrystal plane of the crystal portion;

a first electrode electrically connected to the semiconductor layer ofthe first conduction type; and

a second electrode formed on the semiconductor layer of the secondconduction type on the crystal portion and electrically connected to thesemiconductor layer of the second conduction type.

In a further embodiment, the present invention provides a method ofmanufacturing an integrated semiconductor light emitting deviceincluding a plurality of integrated semiconductor light emittingelements each having: a semiconductor layer of a first conduction typewhich is formed on a major surface and includes a convex crystal portionhaving an inclined crystal plane exhibiting a substantially convex planeas a whole; at least an active layer and a semiconductor layer of asecond conduction type which are sequentially layered at least on theinclined crystal plane of the crystal portion; a first electrodeelectrically connected to the semiconductor layer of the firstconduction type; and a second electrode formed on the semiconductorlayer of the second conduction type on the crystal portion andelectrically connected to the semiconductor layer of the secondconduction type, comprising:

growing a first semiconductor layer of the first conduction type on asubstrate;

forming a growth mask having openings at predetermined positions on thefirst semiconductor layer;

selectively growing a second semiconductor layer of the first conductiontype on the first semiconductor layer exposed through the openings inthe growth mask; and

sequentially growing at least the active layer and the semiconductorlayer of the second conduction type to cover the second semiconductorlayer.

In an embodiment, an image display device is provided including aplurality of semiconductor light emitting elements each comprising:

a semiconductor layer of a first conduction type which is formed on amajor surface and includes a convex crystal portion having an inclinedcrystal plane exhibiting a substantially convex plane as a whole;

at least an active layer and a semiconductor layer of a secondconduction type which are sequentially layered at least on the inclinedcrystal plane of the crystal portion;

a first electrode electrically connected to the semiconductor layer ofthe first conduction type; and

a second electrode formed on the semiconductor layer of the secondconduction type on the crystal portion and electrically connected to thesemiconductor layer of the second conduction type.

In an embodiment, the present invention provides a method ofmanufacturing an image display device integrating a plurality ofintegrated light emitting elements each having a semiconductor layer ofa first conduction type which is formed on a major surface and includesa convex crystal portion having an inclined crystal plane exhibiting asubstantially convex plane as a whole; at least an active layer and asemiconductor layer of a second conduction type which are sequentiallylayered at least on the inclined crystal plane of the crystal portion; afirst electrode electrically connected to the semiconductor layer of thefirst conduction type; and a second electrode formed on thesemiconductor layer of the second conduction type on the crystal portionand electrically connected to the semiconductor layer of the secondconduction type, comprising:

growing a first semiconductor layer of the first conduction type on asubstrate;

forming a growth mask having openings at predetermined positions on thefirst semiconductor layer;

selectively growing a second semiconductor layer of the first conductiontype on the first semiconductor layer exposed through the openings inthe growth mask; and

sequentially growing at least the active layer and the semiconductorlayer of the second conduction type to cover the second semiconductorlayer.

In an embodiment, the present invention provides an illuminating devicehaving a single semiconductor light emitting element or a plurality ofintegrated semiconductor light emitting elements each comprising:

a semiconductor layer of a first conduction type which is formed on amajor surface and includes a convex crystal portion having an inclinedcrystal plane exhibiting a substantially convex plane as a whole;

at least an active layer and a semiconductor layer of a secondconduction type which are sequentially layered at least on the inclinedcrystal plane of the crystal portion;

a first electrode electrically connected to the semiconductor layer ofthe first conduction type; and

a second electrode formed on the semiconductor layer of the secondconduction type on the crystal portion and electrically connected to thesemiconductor layer of the second conduction type.

In an embodiment, the present invention provides a method ofmanufacturing an illuminating device having a single semiconductor lightemitting element or a plurality of integrated semiconductor lightemitting elements each including: a semiconductor layer of a firstconduction type which is formed on a major surface and includes a convexcrystal portion having an inclined crystal plane exhibiting asubstantially convex plane as a whole; at least an active layer and asemiconductor layer of a second conduction type which are sequentiallylayered at least on the inclined crystal plane of the crystal portion; afirst electrode electrically connected to the semiconductor layer of thefirst conduction type; and a second electrode formed on thesemiconductor layer of the second conduction type on the crystal portionand electrically connected to the semiconductor layer of the secondconduction type, comprising:

growing a first semiconductor layer of the first conduction type on asubstrate;

forming a growth mask having an opening at a predetermined position onthe first semiconductor layer;

selectively growing a second semiconductor layer of the first conductiontype on the first semiconductor layer exposed through the opening in thegrowth mask; and

sequentially growing at least the active layer and the semiconductorlayer of the second conduction type to cover the second semiconductorlayer.

In an embodiment, each inclined crystal plane forming a substantiallyconvex plane as a whole may locally include a flat plane.

According to the invention having the above-summarized configuration,the semiconductor layer of the first conduction type is selectivelygrown under the existence of the growth mask having the opening in apredetermined portion. Thereby, it is possible to make a convex crystalportion having an inclined crystal plane composed of a plurality ofcrystal planes different in angle of inclination to exhibit a goodconvex plane as a whole or having an inclined crystal exhibiting asubstantially convex plane as a whole. Then, by sequentially growing atleast the active layer and the semiconductor layer of the secondconduction type to cover the crystal plane, the light emitting elementstructure can be formed. In this case, the semiconductor layer of thesecond conduction type also has an inclined crystal plane composed of aplurality of crystal planes different in angle of inclination to exhibita good convex plane as a whole, or an inclined crystal plane exhibitinga substantially convex plane as a whole. Therefore, in operation of theelement, light generated from the active layer can be extractedefficiently by reflection at the inclined crystal plane of thesemiconductor layer of the second conduction type, which exhibits theconvex plane or the substantially convex plane. Moreover, in comparisonwith a structure in which the crystal portion has an S-oriented inclinedcrystal plane, the present invention can diminish the size of thecrystal portion and can therefore reduce the size of the light emittingelement structure made by sequentially growing the active layer and thesemiconductor layer of the second conduction type on the crystalportion. Furthermore, since the light extracting direction can be closerto the direction normal to the major plane, light is less subjected toblockage even when a black mask, or the like, is placed in the portionother than the light emitting portion.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription of the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B are a plan view and a cross-sectional view of aconventional GaN-based light emitting diode.

FIGS. 2A and 2B are a plan view and a cross-sectional view forexplaining a manufacturing method of a GaN-based light emitting diodeaccording to an embodiment of the invention.

FIGS. 3A and 3B are a plan view and a cross-sectional view forexplaining the manufacturing method of the GaN-based light emittingdiode according to an embodiment of the invention.

FIGS. 4A and 4B are a plan view and a cross-sectional view forexplaining the manufacturing method of the GaN-based light emittingdiode according to an embodiment of the invention.

FIGS. 5A and 5B are a plan view and a cross-sectional view forexplaining the manufacturing method of the GaN-based light emittingdiode according to an embodiment of the invention.

FIG. 6 is a plan view showing an array of openings formed in a mask inthe manufacturing method of the GaN-based light emitting diode accordingto an embodiment of the invention.

FIG. 7 is a scanning electron microscopic photograph of the surfaceconfiguration of a GaN-processed substrate immediately after formationof a light emitting element structure in the manufacturing method of theGaN-based light emitting diode according to an embodiment of theinvention.

FIG. 8 is a scanning electron microscopic photograph of the surfaceconfiguration of a GaN-processed substrate immediately after formationof a light emitting element structure in a manufacturing method of aGaN-based compound light emitting diode taken for comparison with anembodiment of the invention.

FIG. 9 is a scanning electron microscopic photograph of the surfaceconfiguration of a GaN-processed substrate immediately after formationof a light emitting element structure in the manufacturing method of theGaN-based light emitting diode according to an embodiment of theinvention.

FIG. 10 is a scanning electron microscopic photograph of the surfaceconfiguration of a GaN-processed substrate immediately after formationof a light emitting element structure in the manufacturing method of theGaN-based light emitting diode according to an embodiment of theinvention.

FIG. 11 is a cross-sectional view showing distribution of crystallinedefects introduced in the process of growing GaN-based semiconductorlayers forming the light emitting element structure in the manufacturingmethod of the GaN-based semiconductor light emitting diode according toan embodiment of the invention.

FIG. 12 is a cross-sectional view showing an aspect of emission from theGaN-based light emitting diode manufactured by an embodiment of theinvention.

FIG. 13 is a cross-sectional view showing a GaN-based light emittingdiode according to an embodiment of the invention.

FIG. 14 is perspective view of the GaN-based light emitting diodeaccording to an embodiment of the invention, taken from the side of itsn-side electrode.

FIG. 15 is a perspective view showing an image display device accordingto an embodiment of the invention.

FIGS. 16A and 16B are a plan view and a cross-sectional view showing aGaN-based light emitting diode according to an embodiment of theinvention.

FIGS. 17A and 17B are a plan view and a cross-sectional view showing aGaN-based light emitting diode according to an embodiment of theinvention.

FIGS. 18A and 18B are a plan view and a cross-sectional view showing aGaN-based light emitting diode according to an embodiment of theinvention.

FIGS. 19A and 19B are a plan view and a cross-sectional view showing aGaN-based light emitting diode according to an embodiment of theinvention.

FIGS. 20A and 20B are a plan view and a cross-sectional view showing aGaN-based light emitting diode according to an embodiment of theinvention.

FIGS. 21A and 21B are a plan view and a cross-sectional view showing aGaN-based light emitting diode according to an embodiment of theinvention.

DETAILED DESCRIPTION

This invention relates to a semiconductor light emitting element,manufacturing thereof, integrated semiconductor light emitting device,manufacturing method thereof, image display device, manufacturing methodthereof, illuminating device and manufacturing method thereof, which areespecially suitable for application to light emitting diodes usingnitride III-V compound semiconductors.

Embodiments of the invention are explained below with reference to thedrawings. In all figures showing embodiments of the invention, common orequivalent components are labeled common reference numerals.

FIGS. 2A and 2B through FIGS. 5A and 5B show a manufacturing method of aGaN-based light emitting diode according to the first embodiment of theinvention, in which the figures numbered with the suffix A are planviews whereas the figures numbered with the suffix B are cross-sectionalviews.

In the first embodiment, first referring to FIGS. 2A and 2B, a sapphiresubstrate 11 having a C+ oriented major surface, for example, isprepared. After the surface of the sapphire substrate 11 is cleaned bythermal cleaning, for example, an n-type GaN layer 12 doped with ann-type impurity such as Si is grown on the sapphire substrate 11 bymetal organic chemical vapor deposition (MOCVD), for example. The n-typeGaN layer 12 is desirably minimized in crystal defects and penetratingdislocations, and a thickness around 2 μm will be enough in most cases.Various techniques are employable for forming a defects-reduced n-typeGaN layer 12. A typical technique first grows a GaN buffer layer or anAlN buffer layer (not shown) on the sapphire substrate 11 at a lowtemperature around 500° C., then raises the temperature to approximately1000° C. to crystallize it, and grows the n-type GaN layer 12 thereon.This technique may be modified to grow an undoped GaN layer after thegrowth of the GaN buffer layer or the AlN buffer layer and to thereaftergrow the n-type GaN layer 12.

In the next step, a SiO2 film, approximately 200 nm, for example, and aSiN film (especially, Si3N4 film), approximately 10 nm thick, are formedsequentially on the entire surface of the n-type GaN layer 12 by CVD,vacuum evaporation, sputtering, or the like, or preferably by plasmaCVD. After that, a resist pattern (not shown) of a predeterminedgeometry is formed thereon by lithography. Then, under the existence ofthis resist pattern as a mask, the SiN film and the SiO2 film are etchedand patterned to a growth mask 14 having openings 13 at positions forforming elements by wet etching using a fluoric acid-based etchant, forexample, or by RIE using an etching gas containing fluorine, such asCF4, CFH3, or the like. Each opening has the shape of a hexagon havingone side normal to the <1-100> or <11-20> orientation. Size D of theopenings is determined to meet the requirement. Usually, it is 2 to 13μm. In this embodiment, it may be 3 μm, for example. FIGS. 2A and 2Billustrate only one opening 13. Actually, however, a plurality ofopenings are formed in an array. FIG. 6 shows an exemplary layout of theopenings 13. In FIG. 6, P denotes the pitch of the openings. The pitch Pis 10 μm or more in most cases. In this embodiment, it may be 14 μm, forexample.

In the next step, as shown in FIGS. 3A and 3B, the n-type GaN layer 15,doped with an n-type impurity such as Si, is selectively grown on then-type GaN layer 12 exposed through the openings 13 in the growth mask14. Growth temperature in this process may be 940° C. Growth rate is setvery high, for example, as high as 11.0 to 11.3 μm/h, in planar growthreduction. In the process of this selective growth, the growth rate maybe lowered by lowering the growth temperature than 940° C. to render thegrowth slower near the interface with the n-type GaN layer 12. However,for the growth of the most part excluding the proximity to the interfacewith the n-type GaN layer 12, the growth temperature is set to 940° C.,and the growth rate is raised to the high rate of 11.0 to 11.3 μm/h inplanar growth reduction. As a result of this selective growth, thesix-sided steeple-shaped n-type GaN layer 15 is obtained. Each of thesix planes of the steeple-shaped n-type GaN layer 15 is composed of aplurality of (typically, a lot of, or innumerable) crystal planesinclined from the major surface of the sapphire substrate 11 bydifferent angles of inclination from each other. However, assume herethat each of the six planes is composed of four crystal planes F1, F2,F3 and F4 and they make a convex inclined crystal plane as a whole. Inthis case, angles of inclination of the crystal planes F1, F2, F3 and F4become smaller from the bottom of the n-type GaN layer 15 toward itsapex. Angle of inclination of the crystal plane F4 of the upper mostportion including the apex is, for example, 62° to 63° whereas angle ofinclination of the crystal plane F1 of the lowermost portion includingthe bottom is, for example, 74° to 82°. All of the crystal planescomposing the generally convex inclined crystal plane can be regarded asS-oriented planes or substantially S-oriented planes. Accordingly, then-type GaN layer 15 is a combination of a plurality of single crystalsslightly different in crystalline orientation from each other. Size ofthe n-typc GaN layer 15 may be determined depending upon therequirement. In this case, however, it is larger than the size of theopening 13. More specifically, it is approximately three times the sizeof the opening 15.

Subsequently to the growth of the n-type GaN layer 15 as explainedabove, as shown in FIGS. 4A and 4B, an active layer 16 of InGaNcompounds, for example, and a p-type GaN layer 17 doped with a p-typeimpurity such as Mg are sequentially grown on the sapphire substrate 11.As a result, the six-sided steeple-shaped n-type GaN layer 15 as well asthe active layer 16 and the p-type GaN layer 17 grown on the inclinedcrystal planes of the n-type GaN layer 15 make a light emitting diodestructure having double hetero structure. After that, Mg in the p-typeGaN layer 17 is activated by annealing in a nitrogen atmospherecontrolled at a temperature around 850° C. Thickness of the active layerand the p-type GaN layer 17 is determined depending upon therequirement. However, thickness of the active layer 16 is preferably 3nm for example (thickness of the active layer 16 after growth usuallyhas some small measure of distribution from the top to the bottom).Thickness of the p-type GaN layer 17 is preferably as thin as possiblewithin the extent adversely affecting the emission property. Forexample, it may be 0.2 μm. If it is 0.05 μm, the operation voltage canbe reduced to 3 V or less. Growth temperatures of these GaN-basedsemiconductor layers are controlled in the range of 650 to 800° C., morespecifically at 740° C. for example, in case of the active layer 16. Incase of the p-type GaN layer 17, growth temperature is set to a ratherhigh temperature within the extent not adversely affecting the propertyof the active layer 16, namely in the range of 880 to 940° C., and morespecifically at 900° C., for example. The active layer 16 may becomposed of either a single layer of InGaN, for example, or amulti-quantum well structure alternately stacking two InGaN layersdifferent in In composition, for example. The In composition isdetermined depending upon the intended emission wavelength. In thep-type GaN layer 17, Mg concentration of its uppermost layer ispreferably increased to assure good ohmic contact with a p-sideelectrode, explained later. Alternatively, a p-type InGaN layer dopedwith Mg as a p-type impurity, for example, and easy to make ohmiccontact may be grown on the p-type GaN layer 17, and the p-sideelectrode may formed thereon.

Size W of the light emitting structure is approximately 10 μm forexample (see FIG. 4B).

With regard to source materials for growth of the above-explainedGaN-based semiconductor layers, here are used, for example,trimethylgallium ((CH3)3Ga, TMG) as the source material of Ga,trimethylaluminum ((CH3)3Al, TMA) as the source material of Al,trimethylindium ((CH3)3In, TMI) as the source material of In and NH3 asthe source material of N. Concerning the dopants, here are used silane(SiH4) as the n-type dopant, and bis(methyl cyclopentadienile)-magnesium((CH3C5H4)2Mg) or bis(cyclopentadienile)-magnesium ((C5H5)2Mg) as thep-type dopant,

Regarding the carrier gas atmosphere during growth of the GaN-basedsemiconductor layers, a mixed gas of N2 and H2 is used for the n-typeGaN layer 12 and the n-type GaN layer 15. For growth of the active layer16, a N2 gas atmosphere is used as the carrier gas atmosphere. Forgrowth of the p-type GaN layer 17, a mixed gas of N2 and H2 is used. Inthis case, since the N2 gas is used as the carrier gas atmosphere duringgrowth of the active layer 16 and the carrier gas atmosphere does notcontain H2, it is possible to prevent elimination of In anddeterioration of the active layer 16 thereby. Moreover, since the mixedgas atmosphere of N2 and H2 is used as the carrier gas atmosphere forgrowth of the p-type GaN layer 17, the p-type layer can be grown with agood crystallographic quality.

After that, the sapphire substrate 11 having GaN-based semiconductorlayers grown thereon is removed from the MOCVD apparatus.

In the next step, a Ni film, Ag film (or Pt film) and Au film atesequentially deposited on the entire substrate surface by vacuumevaporation, for example. After that, a resist pattern of apredetermined geometry is formed on them by lithography. Under theexistence of the resist pattern as a mask, the Ni film, Ag film and Aufilm are etched. As a result, a Ni/Ag(or Pt)/Au structured p-sideelectrode 18 is formed in the region including the apex of the activelayer 16 and the p-type GaN layer 17 grown on the six-sidedsteeple-shaped n-type GaN layer 15. Size of the p-side electrode 18 isdetermined to minimize the flow of the drive current in the defectiveregion in the n-type GaN layer 15 and others. More specifically, it maybe approximately 4 μm.

In the next step, the growth mask 14 is selectively removed by etchingto expose the n-type GaN layer 12. Thereafter, a Ti film, Pt film and Aufilm are sequentially deposited on the entire substrate surface byvacuum evaporation, and a resist pattern of a predetermined geometry isformed thereon by lithography. Thereafter, under the existence of theresist pattern as a mask, the Ti film, Pt film and Au film are etched.As a result, a Ti/Pt/Au structured n-side electrode 19 if formed incontact with the n-type GaN layer 12.

After that, the substrate having an array of light emitting diodestructures thereon is divided to chips by etching or exfoliation with adicer or excimer laser to obtain the intended GaN-based light emittingdiode. The substrate may undergo an additional process of approximatelyleveling its surface before the substrate having the array of lightemitting diode structures is divided to chips.

The GaN-based light emitting diode, thus obtained, was driven for trialby supplying a current between the p-side electrode 18 and the n-sideelectrode 19. As a result, emission through the sapphire substrate 11was confirmed at an emission wavelength in the range from 380 to 620 nm,for example, at the emission wavelength of 450 nm, depending upon the Incomposition of the active layer. Emission efficiency was high, and theemission output was 40 μW under the drive current of 200 μA, forexample.

Here is explained the angle of inclination of the crystal plane F1 amongthe plurality of crystal planes composing each convex inclined crystalplane of the six-sided steeple-shaped n-type GaN layer 15 in relation tothe emission efficiency. As already explained, the angle of inclinationof the crystal plane Ft is 74° to 82°, for example. Emission efficiencytends to become better as the angle of inclination increases. Forexample, in case the angle of inclination is 74°, when the growththickness of the n-type GaN layer 15 is 2 μm in planar growth reduction,under the size D of the opening 13 being D=10 μm and the pitch P being29 μm, emission efficiency was 100 m/W/A. In case of 76°, when thegrowth thickness of the n-type GaN layer 15 is 2 μm in planar growthreduction, under the size D of the opening 13 being D=3 μm and the pitchP is P=17 μm, the emission efficiency was 200 mW/A. In case of 82°, whenthe growth thickness of the n-type GaN layer 15 is 4 μm in planar growthreduction, under the size D of the opening 13 being D=3 μm and the pitchP is P=17 μm, the emission efficiency was 210 mW/A.

Next explained is the size D and the pitch P of the openings 13 in thegrowth mask 14 shown in FIG. 6 in relation to the emission efficiency.Many samples with combinations (D, P) (in μm) were prepared whilechanging D in the range from 3 to 10 μm and P in the range from 11˜28μm, and the n-type GaN layer 15 was selectively grown on individualsamples. As a result, there was the tendency that the larger the pitchP, the better the inclined crystal planes of the steeple-shaped n-typeGaN layer 15 and the higher the emission efficiency. Regarding the sizeD, there was the tendency that the smaller the size D the higher theemission efficiency. Additionally, it was observed how the light wasextracted, and much light appeared to emit from the entirety, not onlyfrom the central portion of the element but also from the side surfaces.

FIG. 7 shows a photograph of the six-sided steeple-shaped n-type GaNlayer 15 taken by a scanning electron microscope (SEM). The size D ofthe opening 13 in the growth mask 14 is 3 μm, and the pitch P is 10 μm.For comparison, FIG. 8 shows a SEM photograph of a conventionalsix-sided pyramidal n-type GaN layer having S-oriented inclined crystalplanes. Size D of the opening 13 in the growth mask 14 is 10 μm, andpitch P is 29 μm.

In addition, FIG. 9 shows a SEM photograph of an n-type GaN layer 15 incase of the size D of the opening 13 in the growth mask 14 being 3 μmand the pitch P being approximately 17 μm. FIG. 10 shows a SEMphotograph of an n-type GaN layer 15 in case of the size D of theopening 13 in the growth mask 14 being 3 μm and the pitch P beingapproximately 28 μm (note that the scale is ½ of FIG. 9). It isappreciated from FIGS. 9 and 10 that the six-sided steeple-shaped n-typeGaN layer 15 has a higher angle of inclination near the growth mask 14in case the pitch P is approximately 28 μm than in case it isapproximately 17 μm.

According to the first embodiment, the following various advantages canbe obtained.

As shown in FIG. 11, while the n-type GaN layer 15 grows, dislocations20 and depositional defects 21 therein. Some of them extend across theactive layer 16, but they disappear at least in the portion close to theapex of the n-type GaN layer 15. Considering it, the first embodimentdetermines the size of the p-side electrode so that a drive currentsupplied between the p-side electrode 18 and the n-side electrode 19does not flow the defective regions in the n-type GaN layer 15 andothers. Therefore, the first embodiment can provide a GaN-based lightemitting diode remarkably enhanced in emission efficiency and excellentin reliability as well.

Further, the first embodiment grows the six-sided steeple-shaped n-typeGaN layer 15 each composed of a plurality of crystal planes (F1, F2, F3and F4) inclined from the major surface of the sapphire substrate 11 bydifferent angles of inclination from each other to exhibit a convexcrystal plane as a whole, and grows the active layer 16 and the p-typeGaN layer 17 thereon. Thereby, the p-type GaN layer 17 also has inclinedcrystal planes similar to those of the n-type GaN layer 15. Therefore,when a drive current is supplied between the p-side electrode 18 and then-side electrode 19, part of light toward the p-type GaN layer 17 in thelight emitted from the active layer 16 is reflected at the outer surfaceof the p-type GaN layer 17 and travels toward the sapphire substrate 11.On the other hand, part of the light toward inside the n-type GaN layer15 in the light emitted from the active layer 16 directly travels towardthe sapphire substrate 11. As a result, the first embodiment canefficiently extract the light externally from the active layer 16through the sapphire substrate 11, and can enhance the emissionefficiency (see FIG. 12).

Moreover, in the GaN-based light emitting diode according to the firstembodiment, the area occupied by each element can be made very small ascompared with the conventional GaN-based light emitting diode shown inFIGS. 1A and 1B. For example, while the size of the six-sided pyramidallight emitting element structure of the conventional GaN-based lightemitting diode is approximately 20 μm, the size of the six-sidedsteeple-shaped light emitting element structure of the GaN-based lightemitting diode according to the first embodiment is much smaller, namely10 μm approximately.

Furthermore, since the first embodiment uses the Ni/Ag/Au structureincluding Ag having a high reflectance as the p-side electrode 18, thefirst embodiment can enhance the reflectance of the upper part of thesix-sided steeple-shaped p-type GaN layer 17, where the p-side electrode18 is formed. Thereby, the first embodiment can further enhance thelight extracting efficiency and can further enhance the emissionefficiency.

In addition, according to the first embodiment, the light extractingdirection can be made closer to the direction normal to the substratesurface. That is, distribution of emission from a light emitting elementon a plane is usually called Lambertian, or called complete diffusionplane as well. In this case, emission is isotropic from all directions.However, if a black mask, or the like, is provided, light travels alsotoward the black mask. Therefore, to extract light forward, a lens isrequired. The first embodiment, however, can control the lightextracting direction only by controlling the growth.

Next explained is a GaN-based light emitting diode according to thesecond embodiment of the invention.

In the second embodiment, after the layers are grown up to the p-typeGaN layer 17 by the same steps as those of the first embodiment, thep-side electrode 18 is formed on the p-type GaN layer 17. After that,the n-type GaN layer 12 and other upper layers are exfoliated from thesapphire substrate by irradiating a laser beam from the bottom of thesapphire substrate 11 with an excimer laser. Thereafter, the bottomsurface of the exfoliated n-type GaN layer 12 is smoothed by etching,for example, and the n-side electrode 19 is formed on the smoothedbottom surface of the n-type GaN layer 12 as shown in FIG. 13. Then-side electrode 19 may be a transparent electrode made of ITO, forexample. In this case, the n-side electrode 19 can be formed to lie overthe wide area on the bottom surface of the n-type GaN layer 12 includingthe area under the six-sided steeple-shaped structure. In case then-side electrode 19 is a Ti/Pt/Au structured metal laminated film, anopening 19 a is provided in the n-side electrode 19 in alignment withthe six-sided steeple-shaped n-type GaN layer 15 as shown in FIG. 14 topermit light to go out through the n-type GaN layer 12.

The second embodiment assures the same advantages as those of the firstembodiment.

Next explained is an image display device according to the thirdembodiment of the invention. FIG. 15 shows the image display device.

As shown in FIG. 15, the image display device includes GaN-based lightemitting diodes regularly aligned in the orthogonal x and y directionsin a plane of a sapphire substrate 11 to make a two-dimensional array ofGaN-based light emitting diodes. Structure of each GaN-based lightemitting diode may be identical to that of the first embodiment, forexample.

In the y direction, GaN-based light emitting diodes for emitting red(R), GaN-based light emitting diodes for emitting green (G) andGaN-based light emitting diodes for emitting blue (B) are aligned in aclose relation, and three GaN-based light emitting diodes for differentcolors compose one pixel. Individual p-side electrodes 18 of GaN-basedlight emitting diodes for red aligned in the x direction are connectedto each other by wiring 22. Similarly, p-side electrodes 18 of theGaN-based light emitting diodes for green aligned in the x direction areconnected to each other by wiring 23, and p-side electrodes 18 of theGaN-based light emitting diodes for blue aligned in the x direction areconnected to each other by wiring 24. On the other hand, n-sideelectrodes 19 extend in y directions and each functions as a commonelectrode of a series of GaN-based light emitting diodes aligned in they direction.

The simple-matrix image display device having the above-explainedconfiguration can display an image by selecting the wirings 22 to 24 andthe n-side electrodes 19 depending upon a signal of an image to bedisplayed, thereby supplying a current to the selected GaN-based lightemitting diodes of the selected pixel to drive them to emit light.

According to the third embodiment, each GaN-based light emitting diodehas the same configuration as that of the first embodiment and thereforehas high emission efficiency. Thus, a high-luminance full-color imagedisplay device can be realized.

Next explained is an illuminating device according to the fourthembodiment of the invention. The illuminating device has the sameconfiguration as the image display device shown in FIG. 15.

The illuminating device can emit illuminating light by selecting thewirings 22 to 24 and the n-side electrodes 19 depending upon the colorof the illuminating light, thereby supplying a current to the selectedGaN-based light emitting diodes of the selected pixel to drive them toemit light.

According to the fourth embodiment, each GaN-based light emitting diodehas the same configuration as that of the first embodiment and thereforehas high emission efficiency. Thus, a high-luminance full-colorilluminating device can be realized.

Next explained is a GaN-based light emitting diode according to thefifth embodiment of the invention. This GaN-based light emitting diodeis illustrated in FIGS. 16A and 16B.

In the fifth embodiment, the GaN-based semiconductor diode ismanufactured in the same maimer as the first embodiment. However, thefifth embodiment is different from the first embodiment in that the sizeD of the opening 13 in the growth mask 14 is D=10 μm and the pitch P isP=28 μm.

According to the fifth embodiment, since the opening in the growth mask14 has the relatively small size D=10 μm, it diminishes the regionliable to generate dislocations 20 and depositional defects 21 duringselective growth of the n-type GaN layer 15, and thereby reduces adverseinfluence of these crystal defects to emission of light. As a result, aGaN-based light emitting diode enhanced in emission efficiency andreliability can be obtained. For example, when the drive current is 200μA, emission output of 25 μW is obtained. In addition, the fifthembodiment ensures the same advantages as those of the first embodiment.

Next explained is a GaN-based light emitting diode according to thesixth embodiment of the invention. FIGS. 17A and 17B show this GaN-basedlight emitting diode.

In the sixth embodiment, the growth mask 14 having openings 13 is formedin the same manner as the first embodiment. However, unlike the firstembodiment, the size D of the opening 13 is D=10 μm, and the pitch P isP=28 μm. Then, under the existence of this growth mask 14, the n-typeGaN layer 15 is selectively grown. In this process, the growthtemperature is set at 1020° C., for example, and the growth rate is setto 4 μm/h in planar growth reduction. In the process of this selectivegrowth, the growth rate may be lowered by lowering the growthtemperature than 1020° C. to render the growth slower near the interfacewith the n-type GaN layer 12. However, for the growth of the most partexcluding the proximity to the interface with the n-type GaN layer 12,the growth temperature is raised to 1020° C., and the growth rate israised to 4 μm/h in planar growth reduction. After that, the growth iscontinued at the lower growth rate of 0.5 μm/h. As a result, thesteeple-shaped n-type GaN layer 15 grows with inclined crystal planeseach exhibiting a convex plane as a whole as shown in FIGS. 17A and 17B.In this case, the inclined crystal planes comprise M-oriented or lessinclined crystal planes formed on side surfaces of the lower part of then-type GaN layer 15 and S-oriented planes formed on side surfaces of theupper part of the n-type GaN layer 15.

After that, the process is continued in the same manner as the firstembodiment, and the GaN-based light emitting diode shown in FIGS. 17Aand 17B is completed. In this case, size W of the light emitting elementis W=13 μm.

According to the sixth embodiment, the same advantages as those of thefirst and second embodiments can be obtained. For example, when thedrive current is 200 μA, emission output of 25 μW is obtained.

Next explained is a GaN-based light emitting diode according to theseventh embodiment of the invention. FIGS. 18A and 18B illustrate thisGaN-based light emitting diode.

In the seventh embodiment, the growth mask 14 having openings 13 isformed in the same manner as the first embodiment. However, size D ofthe opening 13 is D=10 μm, and the pitch P is P=28 μm. Subsequently,similarly to the first embodiment, the n-type GaN layer 15 isselectively grown under the existence of the growth mask 14, and theactive layer 16 and the p-type GaN layer 17 are grown thereon. In thisembodiment, the active layer 16 has a MQW structure composed of abarrier layer 16 a, well layer 16 b, barrier layer 16 c, well layer 16 dand barrier layer 16 e. The barrier layer 16 a, well layer 16 b, barrierlayer 16 c, well layer 16 d and barrier layer 16 e may be InGaN layers,for example. In this case, size W of the light emitting structure isW=13 μm.

After that, the process is continued similarly to the first embodimentto complete the GaN-based light emitting diode shown in FIGS. 18A and18B.

According to the seventh embodiment, the same advantages as those of thefirst and second embodiments can be obtained. For example, when thedrive current is 200 μA, emission output of 80 μW is obtained.

Next explained is a GaN-based light emitting diode according to theeighth embodiment of the invention. FIGS. 19A and 19B illustrate thisGaN-based light emitting diode.

In the eighth embodiment, the growth mask 14 having openings 13 isformed in the same manner as the first embodiment. However, unlike thefirst embodiment, the size D of the opening 13 is D=10 μm, and the pitchP is P=28 μm. Then, under the existence of this growth mask 14, then-type GaN layer 15 is selectively grown. In this process, the growthtemperature is set at 940° C., for example, and the growth rate is setat a very high rate of 11.0 to 11.3 μm/h in planar growth reduction. Inthe process of this selective growth, the growth rate may be lowered bylowering the growth temperature than 940° C. to render the growth slowernear the interface with the n-type GaN layer 12. However, for the growthof the most part excluding the proximity to the interface with then-type GaN layer 12, the growth temperature is raised to 940° C., andthe growth rate is raised to the very high rate of 11.0 to 11.3 μm/h inplanar growth reduction. After that, the growth is continued at thelower growth rate of 0.5 μm/h. As a result, the steeple-shaped n-typeGaN layer 15 grows in form of a six-sided frustum-shaped steeple havingthe inclined crystal planes each exhibiting a convex plane as a wholeand having a C-oriented or quasi-C-oriented crystal plane on the top ofthe apex portion as shown in FIGS. 19A and 19B. Subsequently, an undopedGaN layer 22 is grown to a thickness around 100 nm to close thesix-sided pyramid on the apex portion of the n-type GaN layer 15 at thegrowth temperature of 940° C., for example and the growth rate of 11.0to 11.3 μm/h. The undoped GaN layer 22 serves as a current-blockingregion.

After that, the process is continued in the same manner as the firstembodiment to complete the GaN-based light emitting diode shown in FIGS.19A and 19B. In this case, size W of the light emitting structure isW=13 μm.

According to the eighth embodiment, the same advantages as those of thefirst and second embodiments can be obtained. Especially, since theundoped GaN layer 22 serves as a current-blocking region and can preventa drive current from flowing through crystallographically inferiorregions, the eighth embodiment attains greater emission efficiency. Forexample, when the drive current is 200 μA, emission output of 80 μW isobtained.

Next explained is a GaN-based light emitting diode according to theninth embodiment of the invention. FIGS. 20A and 20B illustrate thisGaN-based light emitting diode.

In the ninth embodiment, the growth mask 14 having openings 13 is formedin the same manner as the first embodiment. However, unlike the firstembodiment, the opening 13 has the form of an elongated hexagon that mayhave, for example, the maximum size of 30 μm, minimum size of 10 μm inthe direction normal to the direction of the maximum size and the pitchP of 28 μm. Then, under the existence of this growth mask 14, the n-typeGaN layer 15 is selectively grown. In this process, the growthtemperature is set at 940° C., for example, and the growth rate is setat a very high rate of 11.0 to 11.3 μm/h in planar growth reduction. Inthe process of this selective growth, the growth rate may be lowered bylowering the growth temperature than 940° C. to render the growth slowernear the interface with the n-type GaN layer 12. However, for the growthof the most part excluding the proximity to the interface with then-type GaN layer 12, the growth temperature is raised to 940° C., andthe growth rate is raised to the very high rate of 11.0 to 11.3 μm/h inplanar growth reduction. As a result, in a cross-sectional view takenalong the direction of the minimum size of the opening in the growthmask 14, the steeple-shaped n-type GaN layer 15 grows to expand in thedirection normal to the cross section and include inclined crystalplanes each exhibiting a convex plane as a whole, as shown in FIGS. 20Aand 20B.

After that, the process is continued in the same manner as the firstembodiment to complete the GaN-based light emitting diode shown in FIGS.20A and 20B. In this case, size W of the light emitting structure isW=13 μm.

According to the ninth embodiment, the same advantages as those of thefirst and second embodiments can be obtained. For example, when thedrive current is 200 μA, emission output of 80 μW is obtained.

Next explained is a GaN-based light emitting diode according to thetenth embodiment of the invention. FIGS. 21A and 21B illustrate thisGaN-based light emitting diode.

In the tenth embodiment, the growth mask 14 having openings 13 is formedin the same manner as the first embodiment. However, unlike the firstembodiment, the size D of the opening 13 is D=10 μm, and the pitch P isP=28 μm. Then, under the existence of this growth mask 14, the n-typeGaN layer 15 is selectively grown. In this process, the growthtemperature is set at 940° C., for example, and the growth rate is setat a very high rate of 11.0 to 11.3 μm/h in planar growth reduction. Inthe process of this selective growth, the growth rate may be lowered bylowering the growth temperature than 940° C. to render the growth slowernear the interface with the n-type GaN layer 12. However, for the growthof the most part excluding the proximity to the interface with then-type GaN layer 12, the growth temperature is raised to 940° C., andthe growth rate is raised to the very high rate of 11.0 to 11.3 μm/h inplanar growth reduction.

After that, the growth mask is removed by wet etching using a fluoricacid-based etchant, for example, or by RIE using an etching gascontaining fluorine, such as CF4, CFH3, or the like.

Thereafter, an n-type GaN layer (not shown) is grown to a thicknessaround 1 μm, for example, at the growth temperature of 960° C., forexample. Consecutively, the active layer 16 and the p-type GaN layer 17are grown on the clean surface of the n-type GaN layer. In this case,size W of the light emitting structure is W=13 μm.

After that, the process is continued in the same manner as the firstembodiment up to the p-side electrode 18.

Subsequently, a resist pattern (not shown) is formed by lithography tocover the p-type GaN layer 17 in the region excluding the region forforming the n-side electrode. Under the resist pattern as a mask, thep-type GaN layer 17 and the active layer 16 are selectively removed byetching by RIE, for example, to make an opening and expose the n-typeGaN layer 12 through the opening. Thereafter, the resist pattern isremoved. Then, a Ti film, Pt film and Au film are formed sequentially onthe entire substrate surface by vacuum evaporation, for example, and aresist pattern of a predetermined geometry is formed thereon bylithography. Under the resist pattern as a mask, the Ti film, Pt filmand Au film are etched. As a result, the n-side electrode 19 of theTi/Pt/Au structure is formed in contact with the n-type GaN layer 12through the opening formed in the p-type GaN layer 17 and the activelayer 16.

According to the tenth embodiment, the same advantages as those of thefirst and second embodiments can be obtained. For example, when thedrive current is 200 μA, emission output of 25 μW is obtained.

In addition, the tenth embodiment has the following advantages. Asalready explained, the conventional GaN-based light emitting diode needsthe process of selectively growing the six-sided pyramidal n-type GaNlayer having inclined crystal planes inclined from the major surface ofthe substrate on the n-type GaN layer exposed through the opening in thegrowth mask of silicon oxide (SiO2) or silicon nitride (SiN); and theprocess of growing the active layer, p-type GaN layer and others on theinclined crystal plane under the existence of the growth mask retained.However, since the selective growth of the n-type GaN layer and thelater growth of the p-type GaN layer are carried out at a hightemperature of 900° C. or more, there may arise the phenomenon thatsilicon (Si) and oxygen (O) are eliminated from the surface of thegrowth mask and incorporated into layers grown near around during thegrowth. Adverse influences of this phenomenon are especially seriousduring the growth of the p-type GaN layer. It has been found that if Siworkable as an n-type impurity of GaN is incorporated into the p-typeGaN layer while it grows, the intended p-type is difficult to obtain andthat even if a p-type is obtained, both the hole concentration and themobility seriously decrease, thereby disturbing enhancement of theemission efficiency of the light emitting diode. Further, theconventional GaN-based light emitting diode needs the process oflithography for making the opening in the growth mask, and this processneeds the process of bringing the resist into close contact with themask surface to locally remove it. In this removal process, however, theresist is liable to remain in minute gaps of the growth mask and verydifficult to remove. In later growth at a high temperature, any residualresist may become an impurity source and may deteriorate the property ofa p-type GaN layer, or the like. In contrast, in the tenth embodiment,since the growth mask 14 is removed by etching before the growth of theactive layer 16 and the p-type GaN layer 17, the growth mask 14 does notexist when the active layer 16 and the p-type GaN layer 17 are grown.Thus, the tenth embodiment is free from the problem of undesirableincorporation of Si from the growth mask 14 into layers grown thereon,and free from the problem of contamination by the resist. Therefore, thetenth embodiment assures the growth of a sufficiently Mg-doped andlow-resistant p-type GaN layer 17, and enables further enhancement ofthe emission efficiency of the GaN light emitting diode.

Heretofore, specific embodiments of the invention have been explained.However, the invention is not limited to these embodiments butcontemplated various changes and modifications based on the technicalconcept of the invention.

For example, numerical values, materials, structures, shaped,substrates, source materials, processes, and so on, which have beenraised in the explanation of the first to tenth embodiments are nothingbut examples, and other numerical values, materials, structures, shaped,substrates, source materials, processes, and so on, may be used wherenecessary.

More specifically, to enhance the property of the active layer 16 in thefirst to tenth embodiment, for example, an AlGaN layer excellent inlight confinement property may be formed near the active layer 16,and/or an InGaN layer having a small In composition, for example, may beformed. If an effect of diminishing the band gap by so-called bowing isdesirable, Al is added to InGaN to make AlGaInN. Moreover, an opticalguide layer may be interposed between the active layer 16 and the n-typeGaN layer 12 and/or between the active layer 16 and the p-type GaN layer17, if necessary.

Although the first to tenth embodiments use a sapphire substrate, anyother substrate such as a SiC substrate, Si substrate, or the like, maybe used where appropriate. Alternatively, a GaN substrate made by alateral crystal growth technique such as ELO (Epitaxial LateralOvergrowth) or Pendeo may be used.

In the first to tenth embodiments, a contact metal layer of Ni, Pd, Co,Sb, or the like, having a thickness equal to or larger than thewavelength permitting penetration of light generated in the active layer16 may be interposed between the p-type GaN layer 17 and the p-sideelectrode 18. In this case, the effect of enhancing reflection by thecontact metal layer further enhanced the emission efficiency of theGaN-based light emitting diode.

In the third and fourth embodiments, a plurality of GaN-based lightemitting diodes are monolithically formed on the sapphire substrate.However, the GaN-based light emitting diodes monolithically formed onthe sapphire substrate 11 may be divided to discrete elements, thenmounted in the same layout as the third and fourth embodiments on a baseand connected by wirings in the same configuration as explained before.

As described above, according to the invention, the semiconductor layerof the first conduction type is formed on a major surface to include aconvex crystal portion having an inclined crystal plane that comprises aplurality of crystal planes inclined from the major surface by differentangles of inclination to exhibit a convex plane as a whole, or aninclined crystal plane exhibiting a substantially convex plane as awhole. Then, at least on the inclined crystal plane, at least the activelayer and the semiconductor layer of the second conduction type aredeposited sequentially to make the light emitting element structure.Therefore, the invention can provide a semiconductor light emittingelement, integrated semiconductor light emitting device, image displaydevice and illuminating device, which are significantly enhanced inemission efficiency and small in occupied area per each element.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its intended advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

1. A method of manufacturing a semiconductor light emitting elementcomprising: growing a first semiconductor layer of a first conductiontype on a major surface of a substrate; forming a growth mask having anopening at a predetermined position on the first semiconductor layer;selectively growing a second semiconductor layer of the first conductiontype on the first semiconductor layer exposed through the opening in thegrowth mask so as to form a convex crystal portion having an inclinedcrystal plane composed of a plurality of crystal planes inclined fromthe major surface by different angles of inclination to exhibit a convexplane as a whole; and sequentially growing at least an active layer anda semiconductor layer of a second conduction type to cover the secondsemiconductor layer.
 2. The method of manufacturing a semiconductorlight emitting element according to claim 1 wherein the size of theopening in the growth mask ranges from 2 μm to
 13. 3. The method ofmanufacturing a semiconductor light emitting element according to claim1 wherein a growth temperature for the selective growth is controlledand from 920° C. to 960° C.
 4. The method of manufacturing asemiconductor light emitting element according to claim 1 wherein agrowth rate for the selective growth is controlled at 6 pm/h or greater.5. The method of manufacturing a semiconductor light emitting elementaccording to claim 1 wherein a growth rate for the selective growth iscontrolled in a range from 6 pm/h to 18 μm/h.
 6. A method ofmanufacturing an integrated semiconductor light emitting deviceintegrating a plurality of integrated light emitting elementscomprising: growing a first semiconductor layer of a first conductiontype on a major surface of a substrate; forming a growth mask having anopening at a predetermined position on the first semiconductor layer;selectively growing a second semiconductor layer of the first conductiontype on the first semiconductor layer exposed through the opening in thegrowth mask so as to form a convex crystal portion having an inclinedcrystal plane composed of a plurality of crystal planes inclined fromthe major surface by different angles of inclination to exhibit a convexplane as a whole; and sequentially growing at least an active layer anda semiconductor layer of a second conduction type to cover the secondsemiconductor layer.
 7. The method of manufacturing an integratedsemiconductor light emitting device according to claim 6 wherein a sizeof each opening in the growth mask ranges from ¼ to 1 times a size ofeach semiconductor light emitting element.
 8. The method ofmanufacturing an integrated semiconductor light emitting deviceaccording to claim 6 wherein a size of each opening in the growth maskranges from 2 pm to 13 um.
 9. The method of manufacturing an integratedsemiconductor light emitting device according to claim 6 wherein adistance between a nearest two of the openings is equal to or more than10 um.
 10. A method of manufacturing an image display device integratinga plurality of integrated light emitting elements comprising: growing afirst semiconductor layer of a first conduction type on a major surfaceof a substrate; forming a growth mask having openings at a predeterminedposition on the first semiconductor layer; selectively growing a secondsemiconductor layer of the first conduction type on the firstsemiconductor layer exposed through the opening in the growth mask so asto form a convex crystal portion having an inclined crystal planecomposed of a plurality of crystal planes inclined from the majorsurface by different angles of inclination to exhibit a convex plane asa whole; and sequentially growing at least an active layer and asemiconductor layer of a second conduction type to cover the secondsemiconductor layer.
 11. A method of manufacturing an illuminatingdevice having a single semiconductor light emitting element or aplurality of integrated semiconductor light emitting elementscomprising: growing a first semiconductor layer of a first conductiontype on a major surface of a substrate; forming a growth mask having anopening at a predetermined position on the first semiconductor layer;selectively growing a second semiconductor layer of the first conductiontype on the first semiconductor layer exposed through the opening in thegrowth mask so as to form a convex crystal portion having an inclinedcrystal plane composed of a plurality of crystal planes inclined fromthe major surface by different angles of inclination to exhibit a convexplane as a whole; and sequentially growing at least an active layer andthe semiconductor layer of a second conduction type to cover the secondsemiconductor layer.